Motor Overload Trip (Electronic Thermal Relay Function)

What does E.THM mean?

The inverter's electronic thermal O/L relay function detects when the motor is overheating due to excessive load or insufficient cooling, especially during low-speed operation. A pre-alarm (TH) is issued at 85% of the Pr.9 setting, and the inverter output stops when the accumulated heat reaches the trip level. This protection may be insufficient for multiple or special motors, requiring an external thermal relay. Overheating can severely damage the motor windings.

• Continuous motor operation above its nameplate rated current due to sustained mechanical overload.
• Insufficient cooling for the motor (e.g., clogged fan, high ambient temperature, blocked air passages).
• Incorrect electronic thermal relay settings (e.g., P6-01 motor thermal time constant, P6-02 motor overload protection level).
• Motor operating excessively at low speeds without external cooling, leading to reduced fan efficiency.

Click steps to track your progress.

1. 1

   Measure motor current with a clamp meter during operation and compare it to the motor nameplate rated current.

2. 2

   Verify motor cooling fan is operating correctly and cooling fins are clear of obstructions and dust.

3. 3

   Adjust inverter motor thermal relay parameters (e.g., P6-01, P6-02) to accurately match motor characteristics and application.

4. 4

   Inspect the mechanical load for binding, excessive friction, or changes in process demands (e.g., increased material density).

5. 5

   Monitor motor winding temperature using a thermal camera or embedded thermistors (if applicable) during operation.